Abstract
Purpose :
No successful treatment options currently exist to prevent photoreceptor cell death. Our laboratory has shown that reprogramming photoreceptor metabolism via activation of PKM2 is a novel therapeutic strategy for neuroprotection. However, the low aqueous solubility and structural features of the lead compound, ML-265, limit its translational potential. The goal of this study was to develop the next generation of small molecule PKM2 activators, designed specifically for intraocular delivery.
Methods :
Medicinal chemistry efforts identified optimal heterocyclic replacements for the thienopyrrolopyridazinone core of ML-265 based on ClogP values and docking profile in a PKM2 model. Substitutions for the aniline and sulfoxide moieties focused on structurally related heterocyclic systems and solubilizing functional groups, respectively. Solubility of the analogues was tested at pH 7.4. The ability of the analogues to activate PKM2 was tested with recombinant human PKM2, in vitro in 661W cells, and in vivo in rats via intravitreal injections using a continuous, enzyme coupled assay that measures the depletion of NADH via absorbance at 340 nm. To determine efficacy, 661W cells were pre-treated with the novel analogue or vehicle prior to treatment with Fas ligand. Caspase activity and cell viability were measured.
Results :
Analogues of ML-265 were developed with five novel tricyclic core structures. The analogues showed nanomolar potency with recombinant PKM2, and four of these novel cores provided nanomolar potency in vitro in 661W cells. The pyridazinoindolone core (MCTI-313) maintained potency as compared to ML-265 when tested in vivo via intravitreal injections in rats. Treatment with MCTI-313 reduced entrance into the apoptotic cascade and improved cell viability in an in vitro model of outer retinal stress. Thus, structure-activity relationships were explored using this core and various substitutions for the sulfoxide and aniline moieties. Replacing the sulfoxide group with a methoxy group and the aniline moiety with a phenyl group, respectively, maintained potency with recombinant PKM2 and in vitro as compared to ML-265.
Conclusions :
As no other molecules are in the pharmaceutical pipeline or being developed for metabolic reprogramming of photoreceptors, this study is the first to develop the next generation of novel, structurally diverse, PKM2 activators for intraocular delivery.
This is a 2020 ARVO Annual Meeting abstract.